Our goal is to design and build a new hearing aid system, which mitigates the most common complaints that hearing aid users have. The most frequently cited complaints include difficulty understanding speech in multi-talker situations, poor sound quality, dislike of the sound of their amplified voice, and unwanted whistling sounds caused by acoustic feedback. Current efforts, with limited success, use signal processing methods rather than restoring more closely the normal auditory function. There are three key features needed to make this hearing aid a reality that differentiate it from conventional hearing aids. The first is to replace the current acoustic transducer with a non-acoustic mechanical output transducer that directly actuates the tympanic membrane. This transducer, called the EarLens, floats on the tympanic membrane in a manner similar to the way a contract lens floats on the eye. The second is to increase the output bandwidth of the hearing aid. The third is to place a wide-bandwidth microphone in the ear canal to capture the pinna diffraction cues, in a similar manner to the functioning of a normal ear. Our central hypothesis is that a hearing aid that delivers amplified wide-bandwidth sound and directionally dependent pinna cues with a microphone in an open canal configuration will perform better than conventional hearing aids, especially with the presence of competing talkers. In this phase II SBIR application four specific aims are proposed. All hearing aids require a "frequency-gain" prescription. However, current prescription methods are limited to frequencies below 6 kHz and the criteria for fitting have been limited to providing audibility and comfort with no considerations being made to preserve sound localization cues. To address these issues, a new high- frequency fitting prescription will be developed using a loudness model and tested on hearing-impaired subjects. In Specific Aim # 2, an initial EarLens system prototype will be bilaterally fit on hearing-impaired subjects. Proposed measurements include: (1) functional gain at audiometric frequencies between 0.125 to 10 kHz;(2) "spatial release from masking" or the ability to discern a target speech in the presence of symmetrically separated multi-talker maskers;(3) the "better ear advantage" in which the target and masker are arranged asymmetrically such that the target lies closer to one ear than the other. The latter two experiments are conducted with EarLens configured to only amplify sounds over specific bandwidths, which will range from 4 to 10 kHz. For Specific Aim # 3, we seek to build a behind-the-ear (BTE) prototype suitable for an external clinical trial - the "alpha prototype". A number of design changes including industrial design, mechanical design, user interface, and cable design are proposed. And in Specific Aim #4, a clinical trial of the EarLens hearing system will be conducted at four clinical sites located around the country. The objective of the clinical trial is to obtain sufficient data for a 510(k) submission to the FDA upon completion of the work proposed in this application. Most of the six million hearing aid owners in the US report various amplification problems. Our goal is to design a high fidelity open canal hearing aid that more closely relates to normal auditory function thereby providing the brain with critical cues so that it is able to segregate sounds originating from different directions and thus allow the listener to hear selectively and be able to understand desired speech from interfering speech. As an outcome of this approach, it is expected that there will be greater satisfaction with usage of the proposed hearing aid than those currently on the market.